Effect of recovery methods on the oxidative and physical stability of oil body emulsions

Abstract

Three natural oil body emulsions of a similar fat content (∼5%), but differing in their protein composition were obtained from an aqueous maize germ extract. The first was prepared by concentrating the aqueous oil body extract with ultrafiltration to a fat content of ∼5%. The other two were prepared by initially recovering the oil bodies from the extract by centrifugation, either in the presence of sucrose or by applying isoelectric precipitation at pH 5.0 and then diluting the resulting oil body creams with deionized water. The oxidative and physical stability of the three emulsions, either as they were or after submission to thermal treatment (100°C for 15min), were studied following storage at 45°C. The emulsions differed both in their oxidative and physical stability, depending on the recovery method that in turn influenced their continuous phase and/or interfacial membrane protein and/or polar antioxidant composition. Ultrafiltration resulted in the most stable emulsion. Mixtures of the natural oil body emulsions with green tea extracts, aiming to serve as a base for functional beverages, were then prepared and studied for their creaming behaviour. The green tea polyphenols seem to interact with the oil bodies leading to intensive dispersion destabilisation which, however, was halted following carrageenan addition at a relatively very low level.